The present invention relates to an photometer for use in measuring biochemical or biological reaction accompanying changes in absorbance such a s enzyme reaction and the like, more specifically to one for evenly heating the microplate separately adding a test sample in wells and maintaining the temperature so that no temperature difference is present between wells.
As illustrated in FIG. 4(a), (b) and (c), a test sample 14 is added to each well 11 in a microplate comprising a lid part 15 made from a transparent synthetic resin and a wells part 12 made from a transparent synthetic resin and having a plurality of wells 11 inter-coupled with a plate member 10. The microplate is evenly heated to accelerate enzyme reaction and the like. Monochromatic lights with various wave lengths are transmitted to the test sample 14 during or after reaction to measure the absorbance of the test sample 14 in each well 11. Then, the biochemical or biological measurements such as the enzyme activity or quantitative measurements of the substrate in the test sample 14 are carried out based on the measured absorbance.
In other words, as illustrated in FIG. 6, a monochromatic light source 3 and a light detector 4 face each other. A microplate 1 containing the test sample 14 during or after reaction placed on a carrier 5 is transported between the light source 3 and the light detector 4. All test samples 14 in the wells 11 in the microplate 1 are scanned to measure absorbance and the absorbance values are related to the biochemical or biological reaction.
It is to be noted here that accurate and reproducible data cannot be obtained unless the absorbance measurements are carried out by maintaining the temperature of each test sample 14 in each well 11 in the microplate 1 even and constant. Otherwise, the reaction temperature condition differs for each test sample 14 in each well 11.
For this end, temperature control means are proposed to use a fan to enforcedly circulate warmed air so that the microplate 1 is evenly heated and maintained at constant temperature region without causing any temperature difference between wells.
However, in circulating warmed air within a chamber using a fan to stir air over the microplate 1, air flow on the surface of the microplate 1 partly differs; faster at the circumference and slower at the center portion.
This results in faster temperature rise at the circumference of the microplate 1 but slower at the center portion when the temperature of the microplate 1 in a chamber is to be raised by circulating the air. As a result, temperature difference between the test samples 14 in wells 11 in the microplate 1 is caused, thereby making it very difficult to obtain accurate and reproducible data due to uneven reaction temperature.